How to create new plugin

Hi guys,
I changed nopcommerce 4.2 source code to add new section to customer for add product limit for each customer and it works properly. My question is How to create plugin from new codes for doing same operation?

Please follow the NopCommerce documentation for getting started with the plugin development https://docs.nopcommerce.com/developer/plugins/how-to-write-plugin_4.20.html.
This is by no means adequate for building the plugins you are looking for but it should give you the head start in the right direction.

Thanks for reply,
I saw that page. I change source code to show this section in customer->edit, i want know how to create plugin to show like this?
https://pasteboard.co/IKJnBwR.png

for example this:

var menuItem = new SiteMapNode()
{
  SystemName = "Misc.BulkEditProducts",
  Title = "Bulk Edit Products",
  ControllerName = "BulkEditProducts",
  ActionName = "List",
  Visible = true,
  RouteValues = new RouteValueDictionary() { { "area", "Admin" } },
  IconClass = "fa-dot-circle-o"
};
var pluginNode = rootNode.ChildNodes.FirstOrDefault(x => x.SystemName == "Catalog");
if (pluginNode != null)
  pluginNode.ChildNodes.Add(menuItem);
else
  rootNode.ChildNodes.Add(menuItem);

add menu item in catalog, but i need add section to customer->edit page.